I would suggest not getting too fancy with data entry and SharePoint. I just got off the tail end of having to choose between custom built wrappers over top of doing essentially what you get for free from SharePoint because the data entry is simple. SharePoint is not about data entry, it’s a collaboration platform and I wouldn’t try to morph it into something it isn’t. There was another blog I read recently (can’t remember where) but there was a reason why the NewForm and EditForm (and the ListFormWebPart that is used on these pages) isn’t setup for modification (i.e. don’t put any custom web parts on it) and why there’s no Modify Shared Page menu. Keep it simple or look at alternative technologies (like InfoPath) to do the right job.